Molecular Photoinduced Charge Separation: Fundamentals and Application

We have designed and synthesized a number of donor -acceptor linked systems to elucidate the science of photo -induced charge separation. In particular, porphyrin-fullerene and polymer-fullerene linked molecules have been found to be very useful as model systems for addressing issues in excited -state generation, charge separation, and charge dissociation. We have also proposed a new concept, "dynamic exciton" to estab-lish new comprehensive photochemistry dealing with manip-ulation of locally excited state, charge-transfer state, and charge-separated state involving mutual transformation. Simul-taneously, it is pivotal to adopt time-dependent dynamic effects on electron and spin behaviors entangled with movement of atomic nuclei (i.e., vibration, rotation, and fluctuation) and their collective motion into molecular donor-acceptor systems. Versatile dyes for dye-sensitized solar cells as well as donor/ acceptor molecules for bulk heterojunction organic solar cells have also been tailored toward better understanding the under-lying mechanism as well as improving their photovoltaic per-formances. Meanwhile, giant dipole moment produced from donor-acceptor linked molecules by light has been successfully utilized to regulate the membrane potential of living biological cells. This is the first example of the use of charge-separated state in optogenetics and is promising as neuronal therapy by light.